This question may be slightly theoretical but hopefully someone can provide some insight.
Is there any reason to pay extra money for a factory overclocked video card vs just overclocking by themself? It seems obvious to me that one could just OC the card themself and get very close to the same clock as the factory. But...I wonder if companies like EVGA have already tried to get a stable OC on a card prior to branding it and therefore the chances of you OC'ing the card are reduced. Hopefully that makes sense.
I of course realize that a factory OC card is 'under warranty' but please disregard that for this discussion.
Basically, you are right. But, a factory overclocked card usually came with a better heat dissipation. Thus, gives consumer another degree to squeeze even more cranking on it.
And of course the tested their product before they sell it wouldn't they? For such company to release that kind of product tend to confident that they have made a new standard from the reference card or some sort, but not always be true in some cases. However, they still, most of the times, use a better stuff too aside the heatsink. Like a better PCB, a better design or some sort. And this justifies the price they're asking.
Factory overclocked cards are largely to provide performance boosts to people who aren't willing or able to overclock on their own.
For people who can, they usually offer better coolers than the reference designs. Additionally, the overclocking ability of any given card is a crap shoot, so buying factory overclocked means you're guaranteed at least a certain level of overclocking. You can usually overclock them even farther.
For example, my HD 6950 came factory overclocked to 850 MHz core clock, but I pushed that all the way up to 970 MHz.